Present stand-up exercise equipment provides users with fixed straight-bar or rectilinear hand rails. These hand rails try to accommodate two modes of use; exercise in an upright position similar to that normally used in steady state running, climbing, and stand-up biking; and exercise in a leaning forward position similar to that assumed by an accelerating sprinter. These rectilinear hand rails also attempt to accommodate users with body height differentials of a foot or more.
The rectilinear hand rail accommodates body height differentials most effectively when it is on a slope more vertical than horizontal. However, a slope more horizontal than vertical is required for a rectilinear hand rail to best accommodate both `upright` and `lean forward` modes of use. Present stand-up exercise equipment uses rectilinear hand rails with slope selected as a compromise between that slope best suited for accommodating both `upright` and `lean` use. As with most compromises, the result is inappropriate exercise positions for taller and shorter users. Inappropriate exercise position usually makes a user feel uncomfortable or look ungainly during exercise. Inappropriate exercise position can lead to strains that cause discomfort which continues after the exercise session is over.
More particularly, when stand-up exercising it is desirable to have the hand rail about waste-high so that for stand up exercise the lower arm makes a 90.degree. angle with the upper arm. This translates into a comfort zone angle of between 15.degree. and 55.degree. the angle being that between the lower arm and the horizontal. For lean over exercise it is generally desired to grasp a rail with arms nearly fully extended. Note that for short individuals, grasping a high rail looks and feels awkward while giving little perceived or real sense of security. For tall persons in a stand-up position, his hands cannot reach the rail unless his arms are almost fully extended. This again gives the feel of instability.
In his text book, "Human Factors in Engineering and Design", Ernest McCormick says that the combinations of variables involved make it almost impossible to design a fixed work-surface for people of all sizes. As a result of the complexity of the design problem, McCormick suggests adjustability as a solution and cites a Western Electric adjustable workstation.
It will be appreciated that adjustable hand rails could bring more comfort to a greater range of users and modes of use. However, adjustability involves user instruction, user time and inconvenience, additional cost, and an added potential for structural failure and possible injury. The negatives associated with adjustable rail systems thus outweigh the benefits. As a result, in order to have both tall and short users comfortable using a fixed hand rail system while exercising in either the `upright` or `lean` mode, it is necessary to provide a more accommodating geometry than is presently available.